Question

A cell membrane regulates, which substances can enter and leave the cell based on their size and polarity. Ions cross the cell membrane through which of the following processes?

• A. Simple diffusion
• B. Active transport
• C. Endocytosis
• D. Osmosis
• E. Facilitated diffusion

Answer 1

Answer: (E)

Facilitated diffusion

A. Simple diffusion is the net movement of particles of a substance from a region of greater or higher concentration to a region of lower concentration due to their own intrinsic kinetic energy. In simple words, it is a passive movement of molecules along their concentration gradient.

B. In Active transport, molecules are carried from a region of lower concentration to a region of higher concentration against the concentration gradient with the utilisation of ATP.

C. Endocytosis is a process in which there is engulfing of material by the invagination of cell membrane.

D. Osmosis is the diffusion of water molecules through a semipermeable membrane along the concentration gradient.

E. Facilitated diffusion is the passive movement of molecules along their concentration gradient with the help of membrane proteins known as channel proteins or carrier proteins.

Since ions cross the cell membrane with the help of membrane proteins, it is called facilitated diffusion.

So, the correct answer is 'Facilitated diffusion'.